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Jan. 27, 1931.

M. GILD ERSLEEVE ET AL I ,7

DRILLING DEVICE Filed Nov. 10, 1926 :5 Sheets-Sheet 1 Ma. MM

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Jan. 27, 1931. A. M. GILDERSLEEVE ET AL 1,790,613

DRILLING DEVICE Filed Nov. 10,1926 3 Sheets-Sheet. 2

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Jan. 27, 1931- A. M. GILDERSLEEVE ET AL 1,790,613

iatented Jan. 27, 1931 UNITED STATES PATENT OFFICE ARTHUR M. GILDERSLEEVE AND CHARLES L. DEAN, OF DENVER, COLORADO, ASSIGN- ORS TO THE UNIVERSAL ROTARY BIT COMPANY, OF DENVER, COLORADO, A. CORPO- RATION OF COLORADO DRILLING DEVICE Application filed November 10, 1926. Serial No. 147,415.

This invention relates to drilling devices and aims to provide a drilling devlce WhlCh acts with improved efficiency, has a longer life and will drill through a greater vanety of materials.

The nature of the invention may be readily understood by reference to an embodiment of the invention in the form of a bit for earth and rock drilling, such as oil well drilling,

said bit together with one method of use being.

illustrated in the accompanying drawings.

In said drawings:

Fig; 1 is an elevation of the illustrative bit, detached from the drill stem whichrotates it. As indicated by the arrow the bit-is designed to rotate in a clockwise direction, or, if viewed from its lower end, in a counter clockwise direction. v

Fig. 2 illustrates, in a somewhat diagrammatical fashion, an end view of the bottom of the bit; together with an outline of a section of the hole which the bit drills, indicating the relative location of the bit in the hole. The heavy lines embraced between pairs of concentric dot and dash circles and comprising a part of the circumference of the cutters,-

I -show the location and extent of the contact of the cutter with the material being drilled. The spaces between the concentric dot and dash circles accordingly represent the path of cut of-the respective cutters. The dotted lines associated with the respective cutters indicate the endwise projection of the cutter axes and shafts and their angular position with respect to the center line of the bit. Associated with Fig. 2 are fragmentary elevations (Figs. 2, 2', 2 and 2 of the lower end cutter illustrating a device for removably holding the cutter in place.

Fig. 4 is a vertical section illustrating the contour of the bottom of a hole drilled by the bit, the cutting paths of the respective cutters being clearly indicated.

Fig. 5 is a phantom perspective of the bottom of such hole and a diagrammatic perspective of the respective cutters in their.

proper location,the body of the bit not being shown, for convenience in illustration.

The illustrative rotary bit comprises a bit body 1Q, in this instance of more or less cylindrical outline, provided with a plurality ofboring tools herein represented b wedging cutters 11, some or all of which ave their active cutting edges arranged to travel in different circular paths relative to the axis of rotation of the bit. In the present instance, such paths are at different levels and of different radii (see'Fi s. 4 and 5), that having the greatest radius ing advantageously at the highest level (assuxmng for the present, that the axis of the bit be vertical, as in drilling a vertical hole); and, except for the cutter'whose cutting path radius is the shortest, the paths of the cutters, beginning with the outer path, are successively lower.

The cutting edges of the tools are advantageously arranged at a substantial angle relative to the vertical or axis of the bit and also at an angle (other than a right angle) to the (instantaneous) direction of travel of the cutter, i. e., to the tangent to the path of travel, to engage the rock or other material to be cut with both a wedgin and sliding cut,-thereby increasing the e ciency of the wedging cutting action by which the material 1s chipped or split loose.

In the illustrative bit these wedging cut- .tersare represented by circular discs 12 having conical cutting faces 13, and arranged to rotate on their own axes to facilitate the wedging or chipping action afforded by the angularly disposed cutting edge and to provide .for a continuously changing cutting edge. The sharp cutting edge on the cutters is provided by the termmation' of the conical face 13 with the outer face 14 of the disc, which latter face is shown. flat but of rock or other material and to force them upward and out of the path of the cutter, whence they may be carried away, if desired, as later described. The wedging action of the cutters whereby relatively large pieces of rock and hard material are chipped and split loose, is somewhat analogous to the action of the stone cutters chisel,namely,

the particles of rock are detached by an entering cut which sets up wedging force which split the balance of the material by which a given particle is attached with a much less expenditure of power than if the material were loosened by a continuous cut. This cutting of the discs from the solid material to the clear space above the discs not only minimizes the resistance of the material to the drilling operation but maintains the cutters free from interference and blocking by accumulations of already cut material and saves the ener which would otherwise be wasted in crus ing and grinding already cut material if it were permitted to lodge between the" cutters and the solid or uncut material.

To place the cutting edges of the cutters in the above described favorable position for efficient action and also to leave a clearance between the uncut material and the noncutting portions of the cutters, the axes of the cutters are inclined (forwardly in the direction of rotation) to the vertical on axis of the .bit (in the present bit about twentyfive to thirty degrees) and inclined horizontally or laterally .to the direction of travel of the cutter (to skew the cutter). In the present bit such inclinations effect also an advantageous distribution of work among the cutters. The skewing of a cutter shifts the active cutting edge in or out (as the case may be) from a position directly in front of its axis and results in a tendency for the cutter to rotate on its axis toward the side where the cutting occurs. The inclination to the vertical. and to the direction of travel may and in the present instance does, vary for different cutters (seeFig. 2), depending somewhat on where the cutting edge of the cutter strikes the material, relative to its own axis and that of the bit (see Fig. 4). This inclination of the faces of the discs, moreover, causes them to be self-sharpening,-that is a relatively sharp cutting edge is maintained as the discs wear away.

The bit is here shown with four cutters designated respectively as 15, 16, 17 and 18 in the order of the distance from .the axis of rotation of the bit, of the location of contact of the. respective cutters with the material. That is, the location of contact of cutter 15 is nearest the axis, of the bit, that of cutter 16 is farther out and so on. The number of cutters may be increased or decreased as circumstances require.

The above mentioned rotation of a cutter on its axis may generally be explained by the I tion of the cutter edge; and the other cutters rotate in a clockwise direction because their tangential components are clockwise.

This difference in direction of axial rotation may be explained, in this instance, by the different location of cutter 15 and the inclinatio-n of its axis relative to the axis of the bit, as compared with the other cutters (see Fig. 2). The particular location of cutter 1Y5 and its axis places it in an advantageous position to cut away the material adjacent the center of the hole. It should be noted that in the present bit a small portion of material at the centero-f the hole is not cut away but left in the form of a small knob which serves advantageously to assist in maintainthe position of thecutter relative to the axis I of the bit, i. e., on how much the cutter is skewed relative to its path of cutting.

- Since the path of a cutter is circular in the operation of the present bit, its direction of travel for purposes of the foregoing description may be considered 1ts instantaneous direction, i. e., the direction of the tangent no i to its path of travel at any particular point. For present purposes it is unnecessary to determine whether, when traveling along a curved path, the cutter functions differently than if it traveled along a straight path.

Where, as in the present case, the action of a lower cutter (or cutters, if more than one has a given path of travel) cuts away material which would also lie in the path traveled eventually by a higher cutter or cutters, this circumstance may influence the location of the cutter and its direction of rotation (see Fig. 4). For example, cutter 17 previously cuts away some material which would have fallen in the path of cutter 18 and cutter 16 cuts away some material which would have fallen in the path of cutter 17. This potential overlapping of paths of travel permits the design of a bit in which the work of the respective cutters may be more nearly balanced or equalized, bearing in mind that at least two factors determine the work done by a cutter (or cutters traveling in a given path), namely, the width and circumference of the path of cut. This the Wear on the respective cutters may be more nearly equal-' ized; and the period of service of a set of cutters increased to a maximum.

Furthermore, the inventive bit is so constructed and arranged that the work required of a given cutter may be kept within practical limits by using a larger number of cutters. For example, while a hole of a given diameter might be drilled by a two-cutter bit by making the cutters sufficiently large, each cutter obviously would be required to make a wider cut and in general to do more work than if a larger number of cutters were em- 25 ployed to drill the same hole; and the life of a set of cutters on such a bit would accordingly be considerably less than that of a set of a larger number of cutters collectively doing the same work. Since the loss of time in replacing worn cutters (including, of course, the raising and lowering of the bit) is a very substantial item in drilling cost, a considerable saving may be effected by employing a set of three or more cutters of a smaller and more practical size having collectively a greater life. Such cutters may be arranged on the illustrative bit in such positions and at such inclinations as to result in a practically even distribution of work among such cutters, thereby giving a set of cutters amaximum life.

. in the premnt case the cutters are carried on integral stems or shafts 19 although they may be made to rotate freely t ereon) which stems are carried in cylindrical openings 20;

arranged in the body of the bit to give the axes of the cutters the desired inclination. /Vithin these openings are mounted removable bushings'2l which terminate flush with the outer face of the body of the bit and serve as bearings for the cutter stems. The cutter stems preferably fit loosely within their bushings in order to admit readily (for purposes of lubrication) some of the flushing liquid which is pumped into the hole, as presently explained. Balls 22 represent thrust bearings to receive and withstand without undue friction the thrust against the cutters and the weight of the bit and drill shaft, which in some instances and under some conditions may approximate fifty tons for deep wells. Retainer plates 23 prevent the escape of the balls if the cutter shafts be withdrawn.

The cutters and cutter shaftsare conveniently held in place by releasable means represented, in this instance, by lock pins 24 which project into grooves or recesses 25 in the respective cutter shafts (Fig. 3). The lock pins are held in place, in this instance, by lock springs 26 located in recesses 27 in the body of the bit, and passing, adjacent one end, through holes 28 in the lock pins and being screwed, at 29, adjacent the other end, to the body of the bit. To remove a cutter and its shaft it is necessary simply to raise the lock pin against the pressure of the spring until the end of the pin clears the groove 25 in the cutter shaft.

The upper end of the bit body is slightly tapered and threaded at 30 to screw into the lower end of the drill collar at the end of the hollow drill shaft or stem to which power is supplied to rotate the bit, .according to well known practices. The passage through the hollow drill stem communicates with the interior of the bit through the relatively large central passage 31 in the body of the bit. Branching from the lower end of the passage 31 are a number of smaller holes 32, 33, 34, 35 and 36 whose outlets are arranged to direct the flushing liquid against or adjacent the cutting portions of the respective cutters (see Figs. 1 and 2). During the drilling operation water or a mixture of water and mud, is forced under pressure through the drill stem and the bit body and through the holes 32, to 36 which direct it as described to carry or'fioat away the cuttings and chips as fast as they are loosened; The water and material are carried upwardly around the outer surface of'the bit and drill stem to the surface of the hole. This procedure avoids clogging or ballin up of the bit, for example, bysticky gum 0 which might otherwise accumulate and harden around the cutting discs. ln'this connection, thebit body particularly its lower portion is designed, (see Fig. 1) to provide ample water spaces around and ad'acent the cutters to provide for the escape o the flushing liquid laden with chips and cuttings.

As will be seen clearly by reference to the illustrative form of bit, the thrust or reaction of an outer cutter or cutters may be balanced by other cutters located closer to the axis of the bit. F or example, the radial thrust of cutter 18 is balanced by the resultant, opposite thrusts of cutters 15, 16 and 17 which are closer to the axis of the bit and lower down than cutter 18. Thus a drill of this type may be constructed and arranged to drill a larger hole than the largest diameter of the bit and, therefore, will cut a larger hole than necessary for the passage .of the bit. For example, as shown in Fig. 2, the bit will out a hole whose cross section is represented by the dotted circle 37 whereas the bit will pass through a hole whose cross section is represented by the dotted circle 38. The

difference in diameter of'these circles represents the allowable margin of reduction in diameter of the holebywear on the cutters before removal of the latter becomes desirable, as well as the aggregate space around the body of the bit through which the water and fragments of loosened and cut material are carried upwardly. It is unnecessary wherever this characteristic is embodied in a .bit, to ream the hole Whenever new cutters reamer or the sharp bit) before a sharp bitcould be lowered to the bottom of the hole.

The improved bit will cut rapidly through hard material, such as sandstone, limestone and other rock customarily encountered in drilling deep wells, as well as through softer materials such as clay, shale and gumbo (cutting these softer materials with a slicing action) ,thus avoiding the expensive and time consuming procedure of changing bits whenever the bit is about to pass from hard to soft material, and vice versa. The relatively longer life of the cutters (which may readily be made of the most efficient alloy steel), also reduces the number of times a sharp bit must be provided to drill to a given depth; I

The eificiency of the cutting action of the cutter enables the bit to be operated with less power, thereby greatly reducing the strain on the drill stem (with the consequent increase in its life) and permitting a deeper hole to be drilled within a limited expenditure of power.

Although for purposes of convenience the bit has been described as rotating about a vertical axis, as would be the case in drilling an oil well, for example, it is obvious that it may rotate about any other axis, if used, for example, in drilling a horizontal or an inclined opening.

Obviously the invention is not limited to the details of the illustrative bit or the method of drilling here disclosed, since these may be variously modified. Moreover, it is not indispensable that all features of the invention be used conjointly since various features may be advantageously employed without others) in different combinations and sub-combinations.

Having described one embodiment of our invention, we claim:

.1. A bit for deep well drilliiig through earth and rock comprising in combination a rotatable bit body larger at its lower end than at itsupper end, a plurality of exteriorly located rotatable cutters of frusto-conical shape mounted in the enlarged lower end of the bit body in fixed relation to each other and being inclined so that the cutting edges thereof engage the material to be cut at angles substantially less than 90 and being substantially skewed relative to their direction of travel so as to insure rotation thereof about'their respective axes, said cutters being located at different elevations and at different distances from the center of the bit so as to cut in a plurality of circular paths of varying radii which collectively embrace the effective area to be drilled at the bottom of the hole and being relatively arranged so that the lateral thrust of a given cutter is balanced by other cutters traveling in different paths.

2. Abit for deep well drilling through earth and rock comprising in combiantion a rotatable bit body larger'at its lower end than at its upper end, a plurality of exteriorly located rotatable cutters of frustoconical shape mounted in the enlarged lower end of the bit body in fixed relation to each other and being inclined so that the cutting edges thereof engage the. material to be cut at angles substantially less than 90 and being substantially skewed relative to their direction of travel so as to insure rotation thereof about their respective axes, said cutters being located at different elevations and at different d'stances from the center of the bit so as to cut in a plurality of circular paths of varying radii which collectively embrace the effective area to be drilled at the bottom of the hole and being relatively arranged on the lower end of the bit body so that the cutters traveling in the paths of different radii cooperate to balance the'lateral thrusts of'the cutters on the bit body and thereby maintain the bit body centered in the hole.

3. A bit for deep. well drilling through earth and rock comprising in combination a rotatable bit body larger at its lower end than at its upper end, a plurality of exteriorly located rotatable cutters of frusto-conical shape mounted in'the enlarged lower end of the bit body in fixed relation to each other and being inclined so that the cutting edges thereof engage the material to be cut at angles substantially less than 90, and being substantially skewed relative to their direction of travel so as to insure rotation thereof about their respective axes, said cutters being located at different elevations and at different distances from the center of the bit so as to cut in a plurality of circular paths of varying radii which collectively embrace the bottom of the hole but leaving an upstanding projection at the center of thehole to cooperate in centering the bit, said cutters being relatively arranged on the bit body so that those cutting the paths of smaller diameter cooperate to resist the unbalanced thrust of the cutters which cut in paths of larger diameter. 1

' i veaeie rotary bit body, a plurality of exteriorlly; 10-- cated rotatable cutters of frusto-conical s ape mounted on the lower end oi the bit body in fixed relation to each other, said cutters being arranged to out a pluralit of relatively narrow concentric paths of di erent diameter which collectively cover substantially the bottom of the hole, one of said cutters being arranged to cut a path as closely as practicable to the center of the hole and having its axis inclined outwardly so as to cause the inner portion of its cutting edge to engage the material, the next outer cutter having its axis inclined inwardly to avoid interference with the axis of the inner cutter, and a plurality of cutters beyond the second cutter having their axes inclined outwardly so as to cause the outer portions of their cutting edges to engage the material.

5. A bit for deep well drilling comprising in combination a bit body rotatable about a vertical axis, at least four exteriorly located cutters of frusto-conical shape rotatably mounted at the lower end of the bit body, said cutters being inclined relative to the horizontal to engage the material to be drilled at angles substantially less than 90 thereby to loosen the material with a cutting wedging action, said cutters also being substantially skewed relative to their direction of travel to insure rotation about their own axes during rotation of the bit, said cutters being relatively arranged to cuta plurality of concentric paths collectively covering substantially the bottom of the hole, the second cutter from the center cutting at a lower level 7 than the inner cutter and traveling in a path overlapped by the inner cutter whereby to limit the width of the path cut by the inner cutter, the second cutter from the outside cutting at a lower level than the outside cutter but at a higher level than the third cutter from the outside and in a path overlapped by the outer cutter and overlapping the path traversed by the third cutter from the outside, whereby the paths cut by the outside and second from the outside cutters are limited by the adjacent inside cutters.

In testimony whereof, we have signed our names to this specification.

i? I M. GILDERSLEE.

A CHARLES L. DEAN. 

